Source

File: wp-includes/rest-api/endpoints/class-wp-rest-revisions-controller.php

public function get_item_schema() {
		if ( $this->schema ) {
			return $this->add_additional_fields_schema( $this->schema );
		}

		$schema = array(
			'$schema'    => 'http://json-schema.org/draft-04/schema#',
			'title'      => "{$this->parent_post_type}-revision",
			'type'       => 'object',
			// Base properties for every Revision.
			'properties' => array(
				'author'       => array(
					'description' => __( 'The ID for the author of the object.' ),
					'type'        => 'integer',
					'context'     => array( 'view', 'edit', 'embed' ),
				),
				'date'         => array(
					'description' => __( "The date the object was published, in the site's timezone." ),
					'type'        => 'string',
					'format'      => 'date-time',
					'context'     => array( 'view', 'edit', 'embed' ),
				),
				'date_gmt'     => array(
					'description' => __( 'The date the object was published, as GMT.' ),
					'type'        => 'string',
					'format'      => 'date-time',
					'context'     => array( 'view', 'edit' ),
				),
				'guid'         => array(
					'description' => __( 'GUID for the object, as it exists in the database.' ),
					'type'        => 'string',
					'context'     => array( 'view', 'edit' ),
				),
				'id'           => array(
					'description' => __( 'Unique identifier for the object.' ),
					'type'        => 'integer',
					'context'     => array( 'view', 'edit', 'embed' ),
				),
				'modified'     => array(
					'description' => __( "The date the object was last modified, in the site's timezone." ),
					'type'        => 'string',
					'format'      => 'date-time',
					'context'     => array( 'view', 'edit' ),
				),
				'modified_gmt' => array(
					'description' => __( 'The date the object was last modified, as GMT.' ),
					'type'        => 'string',
					'format'      => 'date-time',
					'context'     => array( 'view', 'edit' ),
				),
				'parent'       => array(
					'description' => __( 'The ID for the parent of the object.' ),
					'type'        => 'integer',
					'context'     => array( 'view', 'edit', 'embed' ),
				),
				'slug'         => array(
					'description' => __( 'An alphanumeric identifier for the object unique to its type.' ),
					'type'        => 'string',
					'context'     => array( 'view', 'edit', 'embed' ),
				),
			),
		);

		$parent_schema = $this->parent_controller->get_item_schema();

		if ( ! empty( $parent_schema['properties']['title'] ) ) {
			$schema['properties']['title'] = $parent_schema['properties']['title'];
		}

		if ( ! empty( $parent_schema['properties']['content'] ) ) {
			$schema['properties']['content'] = $parent_schema['properties']['content'];
		}

		if ( ! empty( $parent_schema['properties']['excerpt'] ) ) {
			$schema['properties']['excerpt'] = $parent_schema['properties']['excerpt'];
		}

		if ( ! empty( $parent_schema['properties']['guid'] ) ) {
			$schema['properties']['guid'] = $parent_schema['properties']['guid'];
		}

		$this->schema = $schema;

		return $this->add_additional_fields_schema( $this->schema );
	}